Infer the range of Math.abs

src/hydrogen-instructions.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 253 matching lines @@
   bool CanBeZero() const { return upper_ >= 0 && lower_ <= 0; }
   bool CanBeNegative() const { return lower_ < 0; }
   bool CanBePositive() const { return upper_ > 0; }
   bool Includes(int value) const { return lower_ <= value && upper_ >= value; }
   bool IsMostGeneric() const {
     return lower_ == kMinInt && upper_ == kMaxInt && CanBeMinusZero();
   }
   bool IsInSmiRange() const {
     return lower_ >= Smi::kMinValue && upper_ <= Smi::kMaxValue;
   }
+  void TruncateToSmi() {

[Sven Panne, 2013/06/07 06:40:54]

I think that "ClampToSmi" is a better name. "Clamping" is the common name for
this kind of operation, "truncation" is more associated with floating point
stuff.

+    lower_ = Max(lower_, Smi::kMinValue);
+    upper_ = Min(upper_, Smi::kMaxValue);
+  }
+  void TruncateToInt32() {

[Jakob Kummerow, 2013/06/07 08:21:05]

Considering that lower_ and upper_ are int32_t, this function is always a no-op.
I don't think we need no-op functions :-)

+    lower_ = Max(lower_, kMinInt);
+    upper_ = Min(upper_, kMaxInt);
+  }
   void KeepOrder();
 #ifdef DEBUG
   void Verify() const;
 #endif
 
   void StackUpon(Range* other) {
     Intersect(other);
     next_ = other;
   }
 
@@ skipping 2353 matching lines @@
           return Representation::Double();
         case kMathAbs:
           return representation();
         default:
           UNREACHABLE();
           return Representation::None();
       }
     }
   }
 
+  virtual Range* InferRange(Zone* zone);
+
   virtual HValue* Canonicalize();
 
   BuiltinFunctionId op() const { return op_; }
   const char* OpName() const;
 
   DECLARE_CONCRETE_INSTRUCTION(UnaryMathOperation)
 
  protected:
   virtual bool DataEquals(HValue* other) {
     HUnaryMathOperation* b = HUnaryMathOperation::cast(other);
@@ skipping 3901 matching lines @@
   virtual bool IsDeletable() const { return true; }
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_